The escalating requirements for high density and performance associated with ultra large scale integration semiconductor wiring demand increasingly sophisticated interconnection wiring formation processes. As device sizes decrease along with interconnect wiring critical dimensions, process windows for plasma etching of interconnect wiring damascene features are increasingly narrowed, leaving little room for error.
In dual damascene formation processes, for example, in a via-first method of formation, a via opening is first formed followed by patterning an overlying trench etching mask and etching the trench overlying the via opening. Prior art processes have proposed various schemes for protecting the via opening from additional etching during the trench etching process. For example, filling the via opening with a plug of protective material prior to forming the trench are among the proposed schemes in the prior art.
Many prior art dual damascene formation processes rely on plasma etchback of the via plug filling material following filling of the via opening. One drawback of prior art processes is the difficulty in precisely controlling the thickness of the plug filling material and the process surface topography following etchback. For example, the plasma etchback process can lead to subsequent difficulties in forming a desired overlying resist thickness for trench patterning, thereby leading to degradation of trench etching mask critical dimensions. For example, following a plasma etchback process, an undesirable process surface topography can lead to undesirable variations in the thickness of a subsequently formed overlying trench patterning resist, thereby leading to variations in surface reflectivity, resist exposure, and consequently, degraded critical dimension control. Moreover, plasma etchback processes are a relatively expensive process in terms of equipment and materials.
There is therefore a need in the semiconductor device integrated circuit processing art to develop an improved dual damascene manufacturing process to provide for via protection in a trench etching process while avoiding loss of critical dimension in the trench patterning process.
It is therefore an object of the invention to provide an improved dual damascene manufacturing process to provide for via protection in a trench etching process while avoiding loss of critical dimension in the trench patterning process, in addition to overcoming other shortcomings and deficiencies in the prior art.